The invention relates to leather working machinery, and more particularly to a machine for cutting a soft leather disc into a leather yarn strand capable of being knit into fabrics similarly to other yarn type products.
There have previously been attempts made to produce a fine leather yarn which is attractive, useful and practicable. See, for example, Arbib U.S. Pat. No. 2,067,895. However, to be practicable for use in garments and other fine knit items, a leather yarn must not only be soft and fine but also must be of precise, consistant dimensions so as to enable the yarn to be knit with knitting machinery. There is disclosed in copending application Ser. No. 807,361, now U.S. Pat. No. 4,131,713, to Leslie P. Barta and William M. Alexander, a leather yarn which meets these requirements, and a method for producing such a leather yarn. There is also disclosed a type of machine for cutting the leather yarn from a leather disc. The machine utilized a smooth-surfaced platform for the leather disc, and a rotatable spindle with prongs for gripping the leather disc centrally from below, so that the leather disc was driven rotatably on the smooth surface with very little friction. A fixed-position cutter was located at the periphery of the leather disc for cutting a fine leather yarn from the peripheral edge of the disc as the disc rotated. A sizing was used on the leather disc prior to cutting, to temporarily stiffen it for the cutting operation, thereby avoiding bunching of the leather disc at the point of cutting and providing a uniform cut strand. Mechanism was provided for advancing the spindle, and thus the entire leather disc, in a radial direction toward the cutting blade as cutting progressed, so that a uniform leather strand continued to be cut until the center of the leather disc reached the blade. The speed of rotation and of advancement of the leather disc were increased as the cutting progressed so that the linear speed of production of the cut leather yarn did not drop off as sharply as the leather disc became smaller and smaller.
While the machine disclosed in the above patent was effective to produce a leather yarn of the desired parameters, the stiffening of the leather by sizing did not completely eliminate the risk of bunching at the cutting blade, in part because the leather disc was required to rotate freely on the smooth surface below. The driving force for rotation of the leather disc was applied only at the center of the disc, remote from the cutting operation, so that when the cutting blade encountered significant resistance, as can be expected to occur due to the fibrous nature of the leather, bunching and/or irregular cutting could often be expected to occur. Stresses generated at the cut were transmitted through the radius of the disc to the driven center, causing stress and stretching undulation. Also, the mechanics of moving the driving spindle toward the cutting blade, as compared to the present invention, were somewhat inefficient.